Citroen Xsara Picasso car won't start

I only owned my Picasso a month before the problem started and it was a beauty to drive.Then one morn i had been on school run and when i got home I locked my car as usual.When it was time to go back out i was surprised to see my car was unlocked.Put key into ignition and it tried to start but just wouldn't ignite! I knew straight away it must have something to do with the key as it was stuck with tape and because it wouldn't lock the car.I tried so many companies to try and get a new key but a big fail.Bbut i did manage to get key tested and was told it was definitely broke!Last attempt was to get car taken to a garage I explained that the key was damaged.Update on car ,it's the BSI unit and was told the key did work!! But there is no way of fixiñg my Picasso as the part that's needed has been discontinued.This is a lovely car and such a shame to scrap.. Does anybody know of any way around this I've been told i cant use the BSI out of another car as its partially coded to the car.
Thank you Traci